1. Field of Invention
The present invention relates to a grommet, and relates in particular to a grommet with which an elongated member, such as a wiring harness, can be securely and easily inserted into and retained at a mounting surface such as a body panel of an automobile.
2. Related Art
Various types of grommets have been proposed that can be used for positioning and securing wiring harnesses that pass through automobile body panels. The present applicant has also proposed such a grommet that comprises: a small-diameter cylinder that is fitted around a longitudinal portion of a wiring harness; a large-diameter cylinder that is fitted into a mounting hole; a tapered cylinder that connects the small-diameter cylinder to the large-diameter cylinder; and a grooved lip and a presser piece that are formed around the outer face of the large-diameter cylinder (conventional art: JP-A-8-212857).
According to this conventional art, the large-diameter cylinder is everted so that its inner face is directed outward, and the circumferential edge of the presser piece is deformed to provide a tapered cylinder for insertion into a mounting hole. Then, when the small-diameter cylinder is in turn inserted into the mounting hole, the force it exerts causes the presser piece and the large-diameter cylinder to return to their original shapes, so that the grooved lip formed around the outer face of the large-diameter cylinder engages the inner edge of the mounting hole opening. As a result, through the application of only a small amount of force the wiring harness can be easily and securely positioned.
According to the conventional art, in order for the grooved lip around the large-diameter cylinder to uniformly engage the inner edge of the mounting hole, a set of tongue shaped pieces longitudinally parallel to the axis of the cylinder must be inserted into the mounting hole.
However, since for this conventional art a structure has not been adopted whereby the individual tongue pieces can be positioned in the center of the mounting hole, the grooved lip may not uniformly engage the inner edge of the mounting hole. A modification to correct this problem is still required.
To resolve this problem, it is one objective of the present invention to provide a grommet that can be used to easily position and secure an elongated member, such as a wiring harness, that passes through automobile body panels.
To achieve this objective, according to a first aspect of the invention, a grommet comprises:
a first cylinder through which an elongated member is to be inserted in order to retain the elongated member in a mounting hole that is formed in a mounting surface;
a second cylinder that is connected via an annular connection provided on the outer face of the first cylinder;
a groove-that is formed along the outer face of the second cylinder; and
a plurality of flanges that are formed radially, extending from a portion between the groove and the connection at the outer face of the second cylinder,
wherein the distal ends of the flanges are collectively tapered by everting the second cylinder so as to direct the inner face toward the exterior, and are inserted into the mounting hole, and
wherein by restoring the original shape of the second cylinder the first cylinder is inserted into the mounting hole and the grooved lip engages the inner edge of the mounting hole.
in addition, as is described in the first aspect, to achieve the objective the grommet of the present invention includes a plurality of guide portions that project outward radially from the outer face of the first cylinder, and are inscribed in the circle formed by the inner edge of the mounting hole. Therefore, when the second cylinder is everted, the flanges can be closely attached to the outer face of the first cylinder, without interfering with the individual guide portions.
The first cylinder need only have an inner diameter that corresponds to the outer diameter of an elongated member, such as a wiring harness, or it may have a slightly smaller inner diameter so that it will press tightly against the elongated member therein. For the first cylinder, the same inner diameter or outer diameter need not be continued longitudinally, and the elongated member may be step-shaped or tapered.
The connection need only be projected toward the diameter from an arbitrary position on the outer face of the first cylinder, and be continued in the circumferential direction. The connection may have, for example, a flat ring shape or a substantially conical shape.
The second cylinder need only have an outer diameter that corresponds to the inner diameter of the mounting hole, and its base end may be connected to the circumferential edge of the connection.
Therefore, the first and the second cylinders may be arranged in a nested shape, or may be continuously positioned, via the connection, in the axial direction.
The first and second cylinders and the connection may be integrally formed by using a synthetic resin that is appropriately flexible and waterproof; however, the components may be formed separately so long as sufficient flexibility and water-resistance are provided by the second cylinder.
Furthermore, multiple flanges need only be provided at predetermined equal or unequal intervals around the circumference of the outer face of the second cylinder. For the flanges, an angle relative to the axis of the second cylinder and the distance projected outward from the outer face of the second cylinder may be selected individually, so that when the second cylinder is everted the distal ends of the flanges are fitted between the guide portions and pressed tightly against the outer face of the first cylinder.
When the guide portions are formed they may be given plate-like shapes arranged parallel to the axis of the first cylinder, or plate- or rod-like shapes that are diametrically arranged around the first cylinder. These guide portions may be positioned at equal intervals, or at arbitrarily determined unequal intervals, around the circumference of the first cylinder, so that the distances projected outward correspond to those set for the flanges, and so that the distal ends of the flanges do not interfere with the guide portions.
That is, when the flanges are radially located at intervals of 90 degrees each with the axis of the second cylinder as the center, the guide portions are relatively located at intervals of 90 degrees with the axis of the first cylinder as the center, and with angle phases of 45 degrees relative to the direction in which the flanges are projected.
Since, in the thus structured grommet, multiple guide portions can be inscribed in the mounting hole, so long as the distances the guide portions project are the same, the first cylinder can be so inserted into the mounting hole that its axis matched the axis of the hole. Further, for the grommet, by everting the second cylinder the flanges, which collectively have a cylindrical shape, can be pressed tightly against the outer face of the first cylinder. Therefore, while the condition exists wherein the axis of the first cylinder matches the axis of the mounting hole, the flanges can be inserted into the mounting hole.
That is, in the grommet, so long as the first and the second cylinders are coaxially arranged, and the distances the guide portions are projected are the same, when the first cylinder is inserted into the mounting hole, the flanges, which collectively have a cylindrical shape, can be inserted into the mounting hole, while the axes are automatically matched.
According to a second aspect of the invention, the flanges are projected around a conical face that is extended toward an open end of the first cylinder.
According to the design of this grommet, the flanges are initially inclined toward the open end of the first cylinder. Thus, compared with when the flanges are projected toward the same flat face that is orthogonal relative to the axis of the second cylinder, the flanges can be collectively formed as a tapered cylinder, without the second cylinder being completely everted.
Furthermore, since for this grommet the flanges are initially inclined toward the open end of the first cylinder, compared with when the flanges are projected toward the same flat face, which is an orthogonal projection relative to the axis of the second cylinder, a projection area along the axis of the second cylinder can be reduced.
That is, for this grommet, since the size of the area occupied on the mounting surface can be reduced when the groove engages the inner edge of the mounting hole, the space available in an automobile body can be utilized effectively.
According to a third aspect of the invention, ribs are formed on the faces of the flanges so that they form continuous projections extending from the bases to the distal ends of the flanges.
In this case, one or both of a first flange face that is directed toward the open end of the first cylinder and a second flange face that is directed toward the open end of the second cylinder can be employed as the flange faces.
The ribs formed along the flange faces may be linear or curved, or may have an angular or a closed curve shape. When a plurality of linear ribs are formed, they may be arranged in parallel, or perpendicularly.
These ribs may be formed by cladding or thinning, in the direction of the thickness, flanges having a predetermined thickness.
For the thus structured grommet, if the ribs are formed on the first and the second faces of the flanges, for example, the first flange face contacts the outer face of the first cylinder via the ribs when the second cylinder is everted. And when in this condition the first cylinder is inserted into the mounting hole, the second face contacts the inner edge of the mounting hole via the ribs.
At this time, when the ribs have a pointed cross section the flanges linearly contact the inner face of the second cylinder or the inner edge of the mounting hole. And when the ribs have a rectangular cross section, the faces of the flanges contact the inner face of the second cylinder or the inner edge of the mounting hole.
For the grommet, in order for the second cylinder to revert to its original shape, the faces of the flanges slide along the inner face of the second cylinder or the inner edge of the mounting hole, linearly or belt shaped.
Specifically, in the thus structured grommet, compared with when the faces of the flanges are flat, the resistance encountered as the tapered flanges are inserted into the mounting hole can be reduced. Further, the contact resistance that is generated between the second cylinder and the flange faces when the second cylinder reverts to its original shape can also be reduced. Therefore, the assembly of the wiring harness can be facilitated.
Furthermore, according to a fourth aspect of the invention, a notch is formed between the ribs and the outer face of the second cylinder.
The ribs may be formed, for example, as substantially inverted C shapes or V shapes around the circumference of the flange face. In this case neither end may not be continued on the outer face of the second cylinder.
When, for the grommet of the invention, the ribs are continuously formed on the base ends of the flanges along the outer face of the second cylinder, if to collect the flanges they are bent toward the outer face of the second cylinder, at the ends of the flanges the ribs are contracted and the resistance of the flanges to bending is therefore increased.
Whereas, for the grommet according to the fourth aspect, since a notch is formed between the ribs and the outer face of the second cylinder, compared with when no notch is formed at the pertinent portions, the resistance of the flanges to bending can be reduced, and the assembly of the wiring harness can be facilitated.
According to a fifth aspect of the invention, the guide portions are provided with ridges parallel to the axis of the first cylinder, and when the second cylinder is everted, the distal ends of the flanges can be located inside a virtual cylinder that contacts the ridges.
And when, in the axial direction of the first cylinder, each guide portion has a substantially pointed or a substantially trapezoidally shaped cross section, linear or plane ridges can be provided.
For the thus arranged grommet, since the ridges are formed for the guide portions, the first cylinder can be moved a predetermined distance along the axis, while the axes of the first cylinder and the mounting hole match. Since the distal ends of the flanges are provided inside a virtual cylinder that contacts each ridge, when the first cylinder is moved along the axis, the distal ends of the flanges pass through the mounting hole and reach the reverse side thereof, while the axes of the first cylinder and the mounting hole match.
That is, with this grommet, when, while the second cylinder is everted, the first cylinder is inserted into the mounting hole and is moved a predetermined distance along the axis, the flanges can be inserted into the mounting hole with the axes matched.
According to a sixth aspect of the invention, a plurality of slits formed in the inner face of the second cylinder extend, from radial positions at the open end, parallel to the axis, and continue for a predetermined distance.
A slit may be a simple cut between a pair of walls that come into close contact, or may be a groove having a substantially V-shaped or a substantially U-shaped cross section.
Generally, when a second cylinder having a flat inner face is to be everted, a recessed inner face having a small diameter is deformed and assumed the shape of a convex outer face having a large diameter, i.e., the tension load is imposed across the entire inner face. Therefore, the deformation resistance of the second cylinder is large, and it is difficult to uniformly evert the second cylinder.
However, according to the grommet of the sixth aspect, since slits are formed at radial positions around the inner face of the second cylinder, when the second cylinder is everted the slits are deformed and their cross sections are extended.
That is, with this grommet, as the slits are deformed the tension load, which is imposed across the entire inner face of the second cylinder when it is everted, is dispersed to a plurality of specific positions, and as a result, the total resistance to deformation is reduced. The second cylinder can therefore be uniformly and easily everted.
Generally, for the grommet in the first aspect, an elongated member, such as a wiring harness, is passed through the first cylinder, and is fixed in place when a filler that is injected into the first cylinder solidifies. Then, the second cylinder is everted, so that its inner face is outside, with an arbitrary line at the connection and extending around the circumference acting as a boundary. The resultant grommet is then shipped or stored.
Since the previously mentioned grommet is so designed that a portion of the connection that serves as a boundary is not purposely provided, the second cylinder, for example, may be everted with a line that is inclined relative to the axis of the connection, and during shipping or storage the portion that corresponds to the boundary of the connection may be returned to its initial shape by a flexible reactive force. In this case, before the grommet is attached to a mounting surface, such as an automobile body panel, the second cylinder must again be reversed.
For a grommet according to a seventh aspect of the invention, a thin wall portion is circumferentially formed either on the outer face or on the inner face of the connection.
The thin wall portion can be, for example, a groove that continues around the circumference of the connection, or it may be multiple recessed portions formed at predetermined intervals around the circumference. The groove or the recessed portions that are formed may in cross section have a substantially semi-circular shape, a substantially V shape, a substantially U shape or a substantially rectangular shape, and may be formed in one or both of the outer and the inner faces of the connection.
For the thus structured grommet, since the thin wall portion is formed circumferentially at the connection, when the second cylinder is everted the thin wall portion acts as the boundary.
Therefore, so long as the thin wall portion of the grommet is formed along a face that is perpendicular to the axis of the connection, the reversion of the second cylinder along a line that acts as a boundary and that inclines relative to the axis of the connection can be prevented. Further, since the flexible reactive force exerted by the thin wall portion is weaker than the other portions of the connection, the reversion of the connection to its original shape during shipping or storage can also be suppressed.
According to an eighth aspect of the invention, the thin wall is formed by using a continuing, circumferential groove. Thus, compared with when multiple recessed portions are formed at predetermined intervals around the circumference of the connection, the portion that serves as the boundary of the connection can be precisely determined.
In order to ship or store the grommet of the first aspect with the second cylinder everted, it is preferable that the second cylinder be easily everted, but that it be easily returned to its original shape after it has been attached to the mounting surface.
When the second cylinder is to be everted, or when the everted second cylinder is returned to its original shape, the grommet is deformed so that the connection is extended circumferentially.
That is, when the outer face of the connection is flat, a portion that purposely induces a diameter-extending deformation is not provided at a specific position on the connection.
In this case, in order to evert the second cylinder or to return the everted second cylinder to its original shape, much force is required to push the joint into the mounting hole until a diameter-extending deformation occurs that causes the entire outer face of the connection to be extended circumferentially.
Whereas, according to a ninth aspect of the invention, the grommet includes a plurality of recessed portions that are formed radially toward the generatrix of the outer face of the connection. The recessed portions open widely toward the second cylinder.
The recessed portions can be made thinner than the other portions by forming a step on the outer face of the connection and by flattening the shape of the interior, or the same thickness as that of the other portions can be provided by forming a step on the outer face of the joint and by forming a raised portion on the inner face.
For the thus structured grommet, since multiple recessed portions are formed in the outer face of the connection, a diameter-extending deformation occurs at a specific portion of the connection when the second cylinder is everted, or when the everted second cylinder is returned to its the original shape. Thus, compared with when the outer face of the connection is flat, only a small amount of force is required to push the connection into the mounting hole.
Since the recessed portions of the grommet are formed radially and open widely toward the second cylinder, the diameter-extending deformation of the connection occurs uniformly.
Since the base ends of the flanges function as partial reinforcing members for the connection, it is difficult for a diameter-extending deformation to occur in the portion that corresponds to the base end of each flange of the connection when the second cylinder is everted or when the everted second cylinder is returned to its original shape.
On the other hand, according to a tenth aspect of the invention, since the recessed portions are formed at portions that correspond to the flanges, a diameter-extending deformation that has little effect on the flanges, i.e., a diameter-extending deformation for portions that are easily extended circumferentially, can be further promoted.
When the grommet of the first aspect is shipped or stored while the second cylinder is everted, the groove, which is substantially U-shaped in cross section, is deformed and has a substantially triangular shape with the opposite ridge lines pressed forcibly together. Thus, it is preferable that provisions be made to facilitate the separation of the ridge lines when the grommet is attached to a mounting surface.
Therefore, according to an eleventh aspect, the grommet includes projecting corners and notches that are provided along ridge lines and that are formed by intersecting a side face of the groove that is directed toward the connection and the outer face of the second cylinder. The projected corners and notches are alternately positioned around the circumference of the second cylinder.
A notch can be a conical face that intersects the side of the groove and the outer face of the second cylinder, or a recessed corner formed like a concave step relative to the side of the groove and the outer face of the second cylinder.
A projected corner and a notch need not have the same length in the circumferential direction of the second cylinder; they may have different lengths.
For the thus arranged grommet, projected corners and notches are alternately positioned along the ridges of the groove. Thus, when the grommet is shipped or stored while the second cylinder is everted, even when a groove having a substantially U shape in cross section is deformed and has assumed a substantially rectangular shape in cross section, only the projected corners on a ridge are closely attached to the other ridge, and gaps are provided between the two ridges at the notches.
That is, when this grommet is to be attached to the mounting surface, the ridges of the groove can be separated more easily than they can when notches are not formed in the ridges of the groove.